Active substances/active substance formulation formulated in aqueous solutions are in some cases subject to instabilities which can lead to reduced efficacy or bioactivity and increased toxicity or intolerance. This applies both to classical pharmaceutical agents and to active substances containing peptides or proteins. The stability of pharmaceutical active substances can be improved by a change in the structure (internally) or by the addition of suitable excipients (externally).
A common method of external stabilization of pharmaceutical active substances is the use of suitable excipients. Excipients which stabilize active substances can be roughly classified as follows: sugars and polyols, amino acids, amines, salts, polymers and tensides.
Sugars and polyols are frequently used as non-specific stabilizers. Their stabilizing effect is attributed mainly, in the case of biological active substances, to “preferential exclusion” (Xie and Timasheff, 1997a, Biophysical Chemistry, 64(1-3), 25-43; Xie and Timasheff, 1997b, Protein Science, 6(1), 211-221; Timasheff, 1993, Annual review of biophysics and biomolecular structure, 22, 67-97). With regard to the choice of sugars, in the case of biological active substances, reducing sugars are in most cases avoided.
Saccharose and trehalose, as non-reducing sugars, are used in preference. Further examples of suitable excipients are glucose, sorbitol and glycerol (Boctor and Mehta, 1992, Journal of Pharmacy and Pharmacology, 44 (7), 600-3; Timasheff, 1993 (supra); Chang et al., 1993 Pharmaceutical Research, 10(10), 1478-83) and Mannitol (Hermann et al. 1996, Pharmaceutical Biotechnology, 9 (Formulation, Characterization, and Stability of Protein Drugs), 303-328; Chan et al. 1996 Pharmaceutical Research, 13 (5), 756-761). Furthermore, it is known that a wide variety of polymers have a stabilizing effect on pharmaceutical active substances, predominantly on proteins, for example, antibodies. Human serum albumin (HAS), which was frequently used in the past, has very good stabilizing and aggregation-inhibiting properties, but has since come to be regarded as unsuitable owing to its potential contamination with “blood-borne” pathogens. Among the polymers known so far, hydroxypropyl-β-cyclodextrin (HP-β-CD) proves especially suitable, since it can safely be administered parenterally. Further examples are high-molecular dextrans (18 to 82 kD), PVP, heparin, gelatines of type A and B and hydroxyethyl starch (HES), heparin, dextran sulphate, polyphosphoric acid, poly-L-glutamic acid, poly-L-lysine.
Alongside sugars and polyols, amino acids can also be used as stabilizers, alone or in combination with other excipients. Amino acids are preferably used in the stabilization of proteins. For example, the addition of histidine, glycine, sodium aspartate (Na-Asp), glutamate and lysine hydrochloride (Lys-HCl) inhibits the aggregation of rhKGF in 10 mM sodium phosphate buffer (pH 7.0) together with 5% mannitol (Zhang et al., 1995 Biochemistry, 34 (27), 8631-41). The combination of amino acids and propylene glycol improves, for example, the structural stability of rhCNTF (Dix et al., 1995, Pharmaceutical Research (Supplement), 12, p.97). Lysine and arginine enhance the thermostability of IL-1R (increase in Tm), whereas glycine and alanine have a destabilizing effect (Remmele et al., 1998 Pharmaceutical Research, 15(2), 200-208).
Furthermore, the stability of pharmaceutical active substances is enhanced by various drying methods. However, drying is mostly performed in the presence of excipients which are intended to maintain the stability of the active substances and improve the properties of the dry powder. A decisive factor in stabilization by drying is the immobilization of the active substance in an amorphous matrix. The amorphous state has high viscosity with low molecular motility and low reactivity. Beneficial excipients must thus be capable of forming an amorphous matrix with the highest possible glass transition temperature, into which matrix the active substance is embedded. The choice of excipients thus depends particularly on their stabilization capacities. However, besides this, factors such as the pharmaceutical acceptability of the excipient and its influence on particle formation, dispersibility and flow property also play a decisive role, especially when spray-drying methods are being used.
Spray-drying represents an especially suitable method of enhancing the chemical and physical stability of peptide-/protein-type pharmaceutical active substances (Maa et al., 1998, Pharmaceutical Research, 15(5), 768-775). Especially in the area of pulmonary therapy, spray-drying is being increasingly used (U.S. Pat. No. 5,626,874; U.S. Pat. No. 5,972,388; Broadhead et al., 1994, J. Pharm. Pharmacol., 46(6), 458-467), since administration by inhalation now represents an alternative, even in the treatment of systemic diseases (WO 99/07340). It is a prerequisite that the mean particle size of the powder is in the range of 1-10 μm, preferably 1-7.5 μm, so that the particles can reach the deeper sections of the lungs and thus the bloodstream. The DE-A-179 22 07 gives an exemplary description of the preparation of such spray-dry particles. In the meantime a large number of methods for the preparation of such powders have been described (WO 95/31479; WO 96/09814; WO 96/32096; WO 96/32149; WO 97/41833; WO 97/44013; WO 98/16205; WO 98/31346; WO 99/66903; WO 00/10541; WO 01/13893; Maa et al., 1998, supra; Vidgrén et al., 1987, Int. J. Pharmaceutics, 35, 139-144; Niven et al., 1994, Pharmaceutical Research, 11(8), 1101-1109).
Also suitable as excipients are sugars and their alcohols (e.g. trehalose, lactose, saccharose or mannitol) and various polymers (Maa et al., 1997, Pharm. Development and Technology, 2(3), 213-223; Maa et al., 1998, supra; Dissertation Adler, 1998, University of Erlangen; Costantino et al., 1998, J. Pharm. Sci., 87(11), 1406-1411). However, the excipients chiefly used have various drawbacks. The addition of trehalose and mannitol, for example, has a detrimental effect on the flow properties of spray-dry formulations (C. Bosquillon et al., 2001, Journal of Controlled Release, 70(3), 329-339). Mannitol is additionally prone to recrystallization when the content is more than 20 per cent by weight (Costantino et al., 1998, supra), with the result that stabilizing effects decrease dramatically. Lactose, a frequently used excipient, certainly improves the flow properties of spray-dry formulations (C. Bosquillon et al., 2001, supra), but is problematic, especially in the formulation of peptide-/protein-containing active substances, since lactose can enter into destabilizing Maillard reactions with peptides/proteins, owing to its reducing property.
In the spray-drying of antibodies without the addition of stabilizers, the native secondary structure regularly develops as a result of dehydration, heat and shear and this leads to dramatic loss of bioactivity. Hydrophobic parts of the antibody, which were previously turned inward, turn outwards in this process. This occurs to a greater extent at the hydrophobic interfaces between the water droplets arising in the course of spray-drying and the air. In addition, antibodies within the aqueous phase aggregate to dimmers or aggregates of a high order. This aggregation is often irreversible. Furthermore, the high temperature at which the proteins are sprayed represents a critical parameter. As a result of the high input of energy there can be destabilization of the peptide bonds and denaturing of the antibody. Furthermore, aggregation of spray-dried antibodies occurs during storage of the powder. The residual water content in the powder, in particular, has negative effects in this regard. Protein aggregates are distinguished by reduced or absent biological activity and increased antigenicity.
Oligosaccharides known as Coupling Sugars with the main components maltosyl sucrose and glucosyl sucrose and lactosucrose are used in foodstuffs. They are used as fillers and dispersing agents together with sweeteners such as aspartame, as moderately sweet components in chewing gums, to stabilize trehalose syrups against crystallization or as so-called NDOs (non-digestible oligosaccharides). An improvement and stabilization of the sweetening quality of asparagyl peptides or of the sweet-sour ratio in drinks containing roughage and sweeteners is also known (US 2003/0059511, EP 1 223 175, DE 199 53 727). The use of oligosaccharides for the stabilization of suspensions of therapeutic proteins and fat or oil bases is also known from U.S. Pat. No. 5,489,577 and EP 0630 651. It is explained that without premixing with the oligosaccharides, with blending and kneading with the hydrophobic, semi-solid masses, the proteins would lose their activity. The stabilization potential during storage, in hydrophilic mixtures or in powders, is not mentioned in any way.
An object of the invention was to make available new excipients/mixtures of excipients for the preparation of pharmaceutical formulations. The corresponding formulations should be distinguished, inter alia, by good long-term stability.
A further object of the present invention was to provide new excipients/excipient mixtures for the preparation of dried pharmaceutical formulations. The corresponding powder-type pharmaceutical formulations should be distinguished by good long-term stability and, if possible, by inhalability.
A further object of the present invention was to provide new excipients/excipient mixtures for the preparation of peptide-/protein-containing pharmaceutical formulations, in particular for such as are produced by spray-drying. The corresponding peptide-/protein-containing pharmaceutical formulations should again be distinguished by good long-term stability and, if possible, by inhalability.
A further object of the present invention was to provide new excipients/excipient mixtures for preparing formulations of therapeutic antibodies or antibody derivatives, especially for those produced by spray-drying. The corresponding antibody-containing pharmaceutical formulations should again be distinguished by good long-term stability and, if possible, by inhalability.
A further object of the present invention was to provide appropriate pharmaceutical formulations for administration by inhalation, whether in the form of a dry powder, a propellent-gas-containing metered dose aerosol or a propellent-gas-free inhalation solution.
The objects forming the basis of the patent are achieved by the following embodiments and by the subject matter/methods disclosed in the patent claims.